Electric fuse.



G. W. DAVIS. ELECTRIC FUSE. APPLICATION FILED APR. 22. 1913.

1,1 30,484, Patented Mar. 2, 1915.

' $2Z0LJVENTOR UNITED sTATEs PATENT OFFICE.

CHARLES W. DAVIS, O'F EDG-EWORTH, PENNSYLVANIA, ASSIGNOR T STANDARD UNDERGROUND CABLE COMPANY, OF PITTSBURGH, PENNSYLVANIA, A. CORPO- through I ELECTRIC FUSE.

Specification of Letters Patent.

Application filed April 22, 1913. Serial No. 762,889.

- To all whom it may concern:

Be .it knownv that I, CHARLES W. DAvIs, residing at Edgeworth, in'the county of A1- legheny and State of Pennsylvania, a citizen of the United States,- have invented or discovered. certain new and useful Improvements in Electric Fuses, of which improvement the following is a specification.

My invention-relates to electric fuses, and particularly to those adapted to be used in connection with high voltage currents.

The blowing of an electric fuse takes place, as is Well known, when the current carried thereby becomes abnormal and dangerous, In addition to this increase in current strength necessary in order to blow the fuse, there is a very rapid rise in the current immediately after such blowing and until the arc is finally broken.

It is the object of my invention to render this double increase in electric currents effective to widen the gap between the adjacent ends of the ruptured or blown fuse strip, there being little if any strain upon the strip up to the time of its blowing. To such an end I provide an electro-magnet in circuit with the fuse strip, and I provide an operative connection between a movable part of such magnet and an end of the fuse strip, the arrangement being such that the magnet exerts a relatively small strain upon the fuse strip while a normal current is passing it, but is effective to quickly widen the gap in the fuse strip upon the blowing thereof. v

In the accompanying drawing, which forms part of my specification, I have illus trated in a single figure one embodiment of my invention.

The figure is a vertical sectional view of a junction box, showing two cables entering therein, the fuse structure connecting the cables being shown partly in elevation and partly in vertical section.

The two cables 1, which enter the junction box 2, are each provided with a terminal structure 3, .comprising, in part, a spring clip 4, electrically connected to the conductor core of the cables. The fuse structure is removably secured to said spring clips, and comprises a frame 5 of insulating material; conducting brackets 6 and 7, secured to the opposite ends of said frame; coil 8 and fuse casing 9, secured to said brackets 6 and 7, respectively; and a movable core 10. Each of said brackets is provided with a collar 11, and with a knife-blade contact 12 adapted to be engaged by the spring clips 4. The coil 8 is mounted within the collar 11 of bracket 6, and is wound by a continuation of the conductor 13, electrically connected to said bracket; while fuse casing 9 is mounted within the collar 11 of bracket 7, the fuse strip 14 extending through such casing. The outer end of the casing 9 is closed by means of a removable plug 19 provided with a contact cap 20 to which the fuse strip 14 is electrically connected, and which in turn is adapted to be engaged by the spring arms 21 secured to the collar 11 of bracket 7.

The path of electrical conductivity between the fuse strip 14 and the bracket 6 is preferably efiected through the core 10. To such an end said core comprises a sleeve of conducting material 15, and a. stranded iron core- 16, the outer end of said sleeve being electrically connected to the fuse strip 14 by means of a stem 17 extending loosely through an opening in the end of the casing 9, and the inner end of said sleeve being electrically connected to the coil 8 by means ofa flexible conductor 18. In order to prevent amaterial strain upon the fuse strip 14 during such time as it is carrying a normal current the stranded iron core 16 of the electro-magnet preferably extends but to the end of the 'coil 8, as will be seen by the termination of the dotted lines at the end of the coil.

As will be readily seen, the several current-carrying conductors are arranged in series, so that a current, in passing from the bracket 6 to the bracket 7 flows through the conductor 13, coil 8, flexible conductor 18, core sleeve 15, stem 17, fuse strip 14, cap 20 and spring arms .2l. passing of a normal current through such conductors, there will of course be a small stress upon the fuse strip 14, the electromagnet is so proportioned that such stress will have no prejudicial effect, but further is so proportioned that the increased current, encountered at the time of the blowing of the fuse, will quickly move the core 10, thereby widening the gap between the ends of the ruptured fuse. In the drawing I While, during the have indicated in dotted lines the position of the core 10 and the flexible conductor 18 after such core has been drawn Within the coil.

While my invention may be effectively employed in various electrical installations, the particular form illustrated herein is well adapted for use in a junction box filled with an arc-dampening fluid.

I claim as my invention:

1. In an electric fuse, the combination of a fuse strip, an electro-magnet comprising 2. In an electric fuse, the combination of a fuse strip, an electro-magnet having a movable core secured to one end of said strip, and the coil of said magnet being in circuit with said strip and adapted to receive said core upon the blowing of said strip, the several convolutions of said coil in the operation of the fuse being immovable with relation to each other.

3. In an electric fuse, the combination of a fuse strip, an electro-magnet having a coil in circuit with said strip, and the core ofsaid magnet being electrically and structurally connected at its opposite ends to said coil and to an end of said strip, the several convolutions of said coil in the operation of the fuse being immovable with re lation to each other.

4. In an electric fuse, the combination of a frame, a pair of terminal contacts secured to said frame, a casing borne by one of said terminal contacts, a fuse strip Within said casing and secured thereto at one end, an electro-magnet having its coil secured to the other of said terminal contacts, the core of said magnet being secured to one end of said fuse strip and movable through said coil, said fuse strip, coil and contact terminals being in a series circuit.

In testimony whereof I have hereunto set my hand.

CHARLES W. DAVIS.

Witnesses PAUL N. CRrr'oHLow, FRANCIS J. TOMASSON. 

